Why "the balance of nature"? -- Resilience -- Temporal variability and the individual species -- The effects of food-web structure -- The variability of the environment -- Nonlinear dynamics, strange attractors, and chaos -- Extinctions -- Species differences and community structure as explanations of why introductions fail -- Patterns in species composition -- Food-web structure and community persistence -- Community assembly : or, why are there so many kinds of communities? -- Small-scale experimental removals of species -- Food webs and resistance -- Changes in total density and species composition -- The consequences of introductions and extinctions -- Multispecies models and their limitations -- Conclusions and caveats.